Messier 50
David Rauwerda

Messier 50 is an open cluster in the constellation Monoceros. An open cluster is a group of up to a few thousand stars that formed from the same molecular cloud.This star formation occurs when the giant molecular cloud thousands of times the mass of the Sun collapses and fragments into bunches and thousands of stars are formed. Open clusters are found only in irregular and spiral galaxies in which star formation is actively occurring. M50 may have been discovered in 1711 by G.D. Cassini but it is named after Charles Messier who independently discovered it again in 1772. The angular size of M50 is roughly 655 ArcSeconds and the linear diameter is 10.162 AU.

Open clusters are by nature randomly organized with no central gravitational pull. The bright blue color reveals the high temperatures of the stars in the cluster. Slightly over 3000 light years away and roughly 20 in diameter, this open cluster is believed to be 78 million years old (Earth is 4600 million), old enough to lose the gas around from which it formed, but still young as evidenced by the bright blue at which the stars burn. The energy necessary to burn at these temperature causes the stars to die relatively quickly with a life of hundreds of millions to a few billion years. By comparison, the red stars in the background and interloping with the cluster could continue burning for well over a few billion years and were around long before the cluster and will be around long after the cluster has burned out.